Conceptual Physics (12th Edition)

by
Hewitt, Paul G.

Published by
Addison-Wesley

ISBN 10:
0321909100

ISBN 13:
978-0-32190-910-7

Chapter 9 - Reading Check Questions (Comprehension): 30

Answer

Variations in the orbit of Uranus that could not be explained by the gravity of then then-known planets led to the discovery of Neptune. Later, variations in the orbits of both Uranus and Neptune led to the discovery of Pluto.

Work Step by Step

This is discussed on page 175.
Recently, in 2016, identical techniques have been used to infer the existence of another planet in our solar system.